No, it's not, but I'd use PSUDII simulator to double check the transient response of any candidate choke. Use the current source load option at 4-5mA, and put in a step change of a milliamp or so. If there's ringing, you'll need to add a little DCR.
Aren't you the brave one! That comment could get you ostracized from the low DCR "cult", I mean "school of thought". 😱
Yes, well, unstable supplies are always preferable to a few ohms of DCR in the supply to a class A stage. Sheesh.😉
Will the hammond 157G work? Its 30H 40mA with DCR595 at http://www.hammondmfg.com/153.htm Plenty of DCR! 😀
If we keep up this line of conversation I have a sinking feeling that someone's going to start channeling messages from an imaginary friend ..........
Cheap LED's
Anyone looking for the large quantity of LED's needed for this project should check Target. They have Philips (60) LED Christmas lights strands for $12 in multi-color & single color. They are 5mm superbrights and are vivid.
Anyone volunteer to do an impedance measurement on these?
😉
(I am going to wait until after Christmas and pick up a few strands. Likely a lifetime LED supply for me.)
Anyone looking for the large quantity of LED's needed for this project should check Target. They have Philips (60) LED Christmas lights strands for $12 in multi-color & single color. They are 5mm superbrights and are vivid.
Anyone volunteer to do an impedance measurement on these?
😉
(I am going to wait until after Christmas and pick up a few strands. Likely a lifetime LED supply for me.)
That's still not very cheap (20 cents each), but sure is convenient. If they go on sale after Christmas, the pricing should be attractive. I'll see if my wife has bought any yet...
One good candidate (thanks Daan!) is Agilent HLMP-6000 submini. 4.6 ohm impedance at 10mA. You'd probably want to be conservative and use a couple extra strings in parallel, but they're also about 20 cents each.
One good candidate (thanks Daan!) is Agilent HLMP-6000 submini. 4.6 ohm impedance at 10mA. You'd probably want to be conservative and use a couple extra strings in parallel, but they're also about 20 cents each.
Nice article Sy! (and good job again Bas).
I would like to see the response and THD at 20Hz, and 20kHz. 1kHz is useless.
Consider adding a phase compensation cap across the feedback resistor, and low-freq compensation between the cathodyne and output tubes. This will allow more feedback.
A really useful stability check is to take the response with no feedback, and then make sure that the response doesn't increase by more than 6dB at any frequency with the feedback connected.
Joel
I would like to see the response and THD at 20Hz, and 20kHz. 1kHz is useless.
Consider adding a phase compensation cap across the feedback resistor, and low-freq compensation between the cathodyne and output tubes. This will allow more feedback.
A really useful stability check is to take the response with no feedback, and then make sure that the response doesn't increase by more than 6dB at any frequency with the feedback connected.
Joel
I got 100 red 5mm LEDs from mouser for $12 including shipping.
They seem to have every color and shape and intensity.🙂
They seem to have every color and shape and intensity.🙂
Interesting - the slope of the line on the datasheet forward current v forward voltage graph http://literature.agilent.com/litweb/pdf/5988-1856EN.pdf
(p12 Fig2 - standard red) suggests around 2 ohms max. Did you measure 4.6 in a test setup?
Using Sy's method I measured the HPLM6000 at 1.5 Ohms but expensive for me to buy here in NZ. The next best was the Fairchild led MV50640 at 3.5 Ohms. See page 18. The leds I bought locally were not suitable even though they were the cheapest. I bought the Fairchild type from Farnell and they worked out quite cheap for one hundred.
kopite,
The plot thickens: 1.5 ohms is about what I would have expected from the data sheet graph.
RS Australia has them at A47c in lots of 100+. Digikey's 100+ price is US24c. I bought a whole bunch from Allied recently but got severely burned by the postage, as they only use UPS. For what they charge I could have arranged personal delivery by Learjet!.
pm
The plot thickens: 1.5 ohms is about what I would have expected from the data sheet graph.
RS Australia has them at A47c in lots of 100+. Digikey's 100+ price is US24c. I bought a whole bunch from Allied recently but got severely burned by the postage, as they only use UPS. For what they charge I could have arranged personal delivery by Learjet!.
pm
I'll trust your measurement. Mine was made with interruptions every minute or two from a sugared-up six year old. You've got me curious enough to run another one...
Hi Stuart, yes please confirm the result, while your here I would like to ask you about the power supply for the amp. I know you are fond of Morgan Jones's book and I wondered if you took into consideration the Q of the power supply in your design?
Thanks,
Phil.
Thanks,
Phil.
Yes, I ran a sim in PSUDII, using a stepped current source as a load. Nice and stable, a smooth exponential with no ringing or over/undershoot.
SY said:
Count your blessings. Before you know it you'll be dealing with a liquored-up sixteen year old. 😀
se